Solid Phase Extraction Issues TRC September 2007 Solid
Solid Phase Extraction Issues TRC September 2007
Solid Phase Extraction (SPE) l l Provides a means for preconcentrating water phase organics to allow lower detection limits without logistically intimidating sample sizes (~20 L equivalent per analyte type- PCBs, PAHs, etc) May show some artifacts of incomplete recovery, depending on a number of factors, e. g. DOC, sample size, collection speed
RMP Collection Methodology l l 100 L sample, pumped at 1. 5 L/min by Infiltrex 300 through wound glass filter (nominal 1 um pore) and columns (2 x 70 g) of XAD 2 resin. Most recent cruise increased volume pumped through filter to increase PBDE signal relative to blanks (no change in pumping speed)
Infiltrex vs Whole Water l 4 L whole water sample vs 100 L Infiltrex particulate (filter) + dissolved (XAD 2)
2004
2005
Bias Trend?
Bias Trend? l l Does not track TSS (SSC) 4 L (liquid-liquid) solvent extraction recovery high for low organics (=tot. PCBs) – l 100 L short contact time = lower recovery? 100 L solid phase extraction high(er) for high organics samples – 4 L solvent volume = limited equilibrium?
Alternatives l Switch to liquid-liquid extraction – – – l Likely accurate for low organics Underestimate for high concentrations PCB/PBDE, PAH, OCP, OPP, backup = 4 L x 5 bottles/site x 22 sites = 110 bottles, 440 L to ship Status quo 100 L SPE- (preferred? ) – – – Maintain awareness of tendencies Considered minimum concentrations More accurate for high concentration samples
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